DIFFERENCES IN DYNAMIC BALANCE SCORES IN ONE SPORT VERSUS MULTIPLE SPORT HIGH SCHOOL ATHLETES

Abstract

Purpose/Background:

Researchers have previously reported on the importance of dynamic balance in assessing an individual's risk for injury during sport. However, to date there is no research on whether multiple sport participation affects dynamic balance ability. Therefore, the purpose of this study was to determine if there was a difference in dynamic balance scores in high school athletes that competed in one sport only as compared athletes who competed in multiple sports, as tested by the Lower Quarter Y Balance Test (YBT-LQ).

Methods:

Ninety-two high school athletes who participated in one sport were matched, by age, gender and sport played, to athletes who participated in the same sport as well as additional sports. All individuals were assessed using the YBT-LQ to examine differences in composite reach score and reach direction asymmetry between single sport and multiple sport athletes. The greatest reach distance of three trials in each reach direction for right and left lower-extremities was normalized by limb length and used for analysis. A two-way ANOVA (gender x number of sports played) was used to statistically analyze the variables in the study.

Results:

No significant interactions or main effects related to number of sports played were observed for any YBT-LQ score (p>0.05). Male athletes exhibited significantly greater normalized reach values for the posteromedial, posterolateral, and composite reach while also exhibiting a larger anterior reach difference when compared to the females. Athletes who participated in multiple sports had similar performances on the YBT-LQ when compared to athletes who participated in a single sport.

Conclusions:

The findings of this study suggest that the number of sports played by a high school athlete does not need to be controlled for when evaluating dynamic balance with the YBT-LQ.

INTRODUCTION

Musculoskeletal injuries are one of the potential negative side effects from exercise.¹ The short-term consequences of musculoskeletal injuries may include reduced playing time and possible loss of an entire season of sports participation, while the long-term impact of musculoskeletal injuries may lead to chronic musculoskeletal problems that limit activity.² With the growing concern over the long term consequences associated with exercise related injuries, many tools have been developed to screen athletes for increased injury risk. The goals of these tools are to identify individuals with increased susceptibility to injury so that intervention programs can be targeted for individuals with an elevated risk of injury.^3,4

The Lower Quarter Y-Balance Test™ (YBT-LQ) protocol, a validated and reliable derivation of the Star Excursion Balance Test, has been used as a mechanism to screen individuals for limitations in dynamic balance.⁵ Poor performance on the YBT-LQ has been associated with elevated risk for non-contact lower extremity injury.⁶ Other researchers have reported decreased dynamic balance in patients who have a history of chronic ankle instability or who are ACL deficient.^7–10 Additionally, several researchers have reported that dynamic balance can be modified with neuromuscular training programs, suggesting that it may be possible to mitigate the elevated injury risk that was identified with the YBT-LQ.^11–15

Currently, there have been no reports that have examined dynamic balance and lower extremity proprioception differences between athletes that participate in a single sport as compared to athletes who participate in multiple sports. It would be expected that athletes that sustain and react to different perturbations through multiple sports could potentially develop varied and adaptable balance strategies. Thus, it would be expected that multiple sport athletes might exhibit improved performance on dynamic balance testing simply due to the factor of multiple sport participation. Therefore, examining the effect of multiple sport participation on balance performance is important, particularly in a high school setting where the athletes are at the greatest risk for injury and also tend to participate in more than one sport.¹⁶

While there are known performance differences on the YBT-LQ across sport, gender, and competition level, there are presently no reports available on the effect of participation in multiple sports on YBT-LQ score.¹⁷ Therefore, the purpose of this investigation was to determine if differences exist in YBT-LQ scores between high school athletes that compete in a single sport as compared to multiple sport athletes. The effect of gender on this relationship was also examined due to the current literature supporting the construct that neuromuscular differences between genders may play a role in the increased risk of injury among female athletes.^18–20

METHODS

Subjects

The subjects recruited for the study were part of a large database of high school athletes who were tested during pre-season physicals for dynamic balance in addition to the standard physical examination. An a-priori power analysis was conducted to determine the minimum number of subjects that would be required to have adequate statistical power. Using α = 0.05 and β = 0.20 and data from a prior study by Herrington and colleagues,¹⁰ it was determined that 15-22 subjects were required in each group to observe a clinically relevant differences in YBT-LQ scores. From the database, ninety-two high school athletes were identified that participated in a single sport that had an adequately matched control who participated in the same sport as well as in one or more additional sports. Subjects were matched, by age, gender (24 female pairs and 68 male pairs) and sport played. Subjects were excluded from the study if they had a lower extremity amputation, vestibular disorder, lack of medical clearance for participation, undergoing treatment for inner ear, sinus or upper respiratory infection or head cold, or cerebral concussion within the previous 3 months. All athletes were free from injury at the time of testing. Unfortunately, no information was available on history of injury for the subjects. Prior to participation all subjects read and signed informed consent forms approved by the Institutional Review Board at the author's university at the time of data collection.

Measures

Lower Quarter Y-Balance Test (YBT-LQ)

YBT-LQ collection occurred using a previously established standardized testing protocol that has shown to be reliable.^5,6 First, the subjects viewed a standard video demonstration followed by six practice trials prior to testing.⁵ Afterwards, all subjects performed the YBT-LQ with shoes off in an effort to decrease the possible influences footwear may have on balance. The subject began the test by standing with one foot on the stance plate with the most distal aspect of the foot at the starting line, and then was asked to reach with the opposite leg in the anterior (Figure 1, forward), posteromedial (Figure 1, back and out to the side of the reaching leg), and posterolateral directions (Figure 1, back and behind the side of the stance leg). The testing order was 3 trials standing on the right foot reaching in the anterior direction (right anterior reach) followed by 3 trials standing on the left reaching in the anterior direction. This procedure was repeated for the posteromedial and then the posterolateral reach directions. During the trials, the reach foot was not allowed to touch down on the floor or gain balance from the reach indicator or support pipe. If the subject was unable to perform the test according to the above criteria in six attempts, the subject failed that direction, no data were collected and another trial was conducted.

Figure 1.

The three reach directions of the Lower Quarter Y Balance Test (a. anterior, b. posteromedial, c. posterolateral).

Reach distance was measured from the most distal aspect of the toes of the stance foot to the most distal aspect of the reach foot in the anterior, posteromedial, and posterolateral directions. The greatest reach of three trials for each direction, for each leg, was used for analysis. Reach distances were normalized to limb length, using the measured distance from the ASIS to medial malleolus in supine. A composite reach score was obtained by taking the average of the normalized reach scores ([Normalized Anterior+ Normalized Posteromedial + Normalized Posterolateral]/3). Reach symmetry was also assessed by obtaining the difference in the absolute reach distance between left and right sides for all reach directions.

Data Analysis

A two-way analysis of variance was used for analysis with gender and sport classification (one vs. multiple) being the two independent factors. The normalized reach scores for the left and right sides were averaged to examine performance for each independent reach directions as well as the composite score between the single and multiple sport athletes as well as the difference between genders. The examination of reach symmetry in all three directions allowed for the independent assessment of left and right comparison. An alpha level of p<0.05 was used to determine statistical significance. All data were analyzed using SPSS for Windows, Version 14.0 (SPSS Inc, Chicago, IL).

RESULTS

Athletes who participated in only one sport were 6 months older on average than athletes who participated in multiple sports (p<0.01, Table 1). No significant differences were observed for height or weight (p>0.05).

Table 1.

Characteristics single sport and multiple sport high school athlete participants.

	Single Sport (n=92)			Multiple Sport (n=92)
Variable	Mean	SD	95% CI	Mean	SD	95% CI	p-value
Age (yrs)	15.9	1.2	15.6 to 16.1	15.4	1.2	15.2 to 15.6	<0.01
Height (cm)	173.2	9.2	171.3 to 175.1	172.9	10.2	170.8 to 175.0	0.90
Weight (kg)	73.7	19.1	69.8 to 77.6	70.5	14.4	67.5 to 73.5	0.19

No significant interaction was found for gender and number of sports played, and there were no main effects for the number of sports played in regards to normalized anterior (p=0.55), posteromedial (p=0.74), posterolateral (p=0.41) or composite reach of the YBT-LQ (p=0.95) (Table 2). Reach symmetry was also compared and there were also no interactions or main effects for the number of sports played for any reach direction (anterior: p=0.20; posteromedial: p=0.56; posterolateral: p=0.23). Interestingly, there was a significant main effect for gender for the normalized posteromedial, posterolateral and composite YBT-LQ scores as well as the anterior difference (p=0.03) (Figure 2 & Figure 3). Males exhibited greater posteromedial (p<0.01), posterolateral (p<0.03), and composite reach (p<0.03) while females exhibited a lower anterior reach difference (p<0.03).

Table 2.

Average reach and symmetry scores for the single sport and multiple sport high school athletes.

	Single Sport (n=92)			Multiple Sport (n=92)
Variable	Mean	SD	95% CI	Mean	SD	95% CI	p-value
Composite Reach Score (%LL)	97.1	8.2	95.4 to 98.8	97.1	8.4	95.3 to 98.8	0.98
Anterior Reach Score (%LL)	75.5	7.1	74.0 to 77.0	76.4	7.9	74.8 to 78.1	0.33
Posteromedial Reach Score (%LL)	108.2	10.3	106.1 to 110.5	109.1	10.2	107.0 to 111.4	0.65
Posterolateral Reach Score (%LL)	107.4	11.4	105.1 to 109.8	105.8	11.1	103.4 to 108.1	0.29
Anterior Difference (cm)	2.8	2.2	2.3 to 3.3	3.6	3.8	2.8 to 4.4	0.09
Posteromedial Difference (cm)	4.6	4.4	3.7to 5.5	4.3	3.8	3.5 to 5.1	0.63
Posterolateral Difference (cm)	4.3	4.3	3.4 to 5.2	5.0	4.2	4.1 to 5.9	0.23

%LL, percent leg length

Figure 2.

Gender differences for the normalized values of the three reach directions along with the composite score of the Lower Quarter Y Balance Test. All data are presented as mean values with the error bars representing the standard deviation. (% LL – percentage of leg length, * - indicates statistical significant differences)

Figure 3.

Gender differences in bilateral asymmetry of the three reach directions on the Lower Quarter Y Balance Test. All data are presented as mean values with the error bars representing the standard deviation. (* - indicates statistical significant differences)

DISCUSSION

The findings from this study suggest that high school athletes who participate in multiple sports do not perform differently on the YBT-LQ than comparable high school athletes who only participate in one sport only. Thus, when evaluating an athlete's performance on the YBT-LQ, the number of sports played by the athlete does not appear to be a significant factor that affects test performance. While not a primary focus of this study, it was also observed that males exhibit greater performance on the YBT-LQ in the posteromedial, posterolateral and composite reach directions when compared to females even when values are normalized for leg length. Conversely, females exhibited reduced anterior reach difference which would be associated with greater reach symmetry.

Performance on the YBT-LQ has been suggested by researchers to vary depending on an individual's competition level, sport, and gender.⁵ Furthermore, previous researchers have also suggested that YBT-LQ performance is affected in individuals with an injury history including an ACL rupture or chronic ankle instability.^7–10 These factors should be considered when evaluating an athlete's performance on the YBT-LQ with regard to identifying athletes at an elevated risk for injury as well as in establishing objectives measures for return to sport criteria. The findings of the current study indicate that the athlete's participation in multiple sports is not a factor that affects their performance on the YBT-LQ.

It was clear from our study that high school males performed better on various reach directions of the YBT-LQ in comparison to high school females. This finding is supported by one prior study²¹ on the Star Excursion Balance Test (SEBT) while one other study observed that females performed better than males on the Star Excursion Balance Test.²² Both of these prior studies had smaller sample sizes and were conducted using college students on the standardized²¹ and abbreviated²² Star Excursion Balance test protocol. As a result there are a number of factors (such as differences in age of the subjects, testing protocol, effect of fatigue) that may have led to the differences in the findings; however, no consistent factors exist of which the authors are aware. However, it does appear that inherent gender differences do exist on the YBT-LQ and SEBT which makes it appropriate to continue to develop normative data that is gender specific. The development of gender specific normative values would be helpful from a rehabilitation standpoint as clinicians aim to use performance data to make decisions regarding the readiness of patients for activity, with minimal risk of re-injury.¹⁷

Several limitations of the current study should be noted. The primary limitation of the study is that there were a disproportionate number of female and male subjects. However, it should be noted that the variability in the male and female scores on the YBT-LQ was similar across the examined for the analyzed measurements. This observation would suggest that any Type II error that may be attributed to lower subject numbers and high levels of variability would be minimal due to the relatively normalized variance between the genders. A second limitation is a lack of injury history on the subjects included in the study. Prior research has suggested that patients with ACL injury or chronic ankle instability perform lower on the SEBT.^7–10 Although these limitations exist, they are not considered to be critical factors that limit the external validity of the study.

Recommendations for Future Research

Current evidence suggests that the YBT-LQ may be a field ready and time-expedient test that can be used to assess lower extremity injury risk in athletes. At the interscholastic level, the diagnostic ability of the YBT-LQ for identifying athletes at an elevated risk for injury has only been examined in basketball, and thus future research should assess the YBT-LQ in different sport high school populations. In addition, as the YBT-LQ grows in its use in youth populations it would be beneficial to understand how performance on the YBT-LQ is affected by maturation and growth. It may be that performance on dynamic balance can highlight when adolescents who are rapidly going through maturation may be at a greater risk for injury due to a lack of dynamic balance and proprioception. Finally, future studies should examine whether the relationships observed in the current study are maintained in different age groups and competition levels.

CONCLUSION

The findings of this study indicate that there is no difference in the YBT-LQ performance in athletes who compete in one sport compared to athletes who compete in multiple sports. In addition, males exhibit increased performance on the YBT-LQ compared to females even when values are normalized to leg length.